The present invention relates to a measuring instrument, which projects a distance measuring light and measures a distance to an object to be measured by receiving a reflected light from the object to be measured.
As one of the measuring instruments, which projects a distance measuring light to the object to be measured, performs a distance measurement and an angle measurement of a measuring point and determines three-dimensional coordinates of the measuring point, a total station is known.
A conventional type total station is mounted on a fixing means such as a tripod or the like, and is installed at a predetermined point via the fixing means. Further, an installment of the total station is attended with a leveling operation in order to obtain a vertical reference.
On a measuring instrument with high accuracy such as the total station or the like, the vertical reference of high accuracy is required. Therefore, a high accuracy tilt sensor is used as a sensor for detecting a horizontality.
The high accuracy tilt sensor can detect the horizontality with high accuracy, but a range of a measurement is narrow, and the range is about 6 arc minutes at most.
For this reason, as a preparation to perform the leveling, an operator performs leveling manually so that the total station will be approximately horizontal, i.e., a tilting of the total station will be within a detection range of the tilt sensor.
Further, with respect to an installing place of the fixing means, there is a restriction that the place must be selected where the total station, as put on, will be approximately horizontal so as to enable to perform leveling, or the like.